Product Description
Seamless TP304, TP321H, and TP347 Stainless Steel Pipes
1. Product Overview
Seamless TP304, TP321H, and TP347 stainless steel pipes are highly sought - after in numerous industries for their reliable performance in transporting fluids and gases. These pipes are crafted from distinct grades of stainless steel, each grade possessing unique chemical and mechanical properties that render them suitable for specific applications. Their seamless construction, achieved through specialized manufacturing processes, ensures enhanced integrity and leak - tightness, making them ideal for critical applications where reliability is paramount.
2. Specifications
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Specification
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TP304
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TP321H
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TP347
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Dimensions
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Available in a broad range of diameters, typically from 1/8" to 48" or even larger for custom - made solutions. Wall thicknesses vary from thin - walled options (around 0.065") for applications with lower pressure requirements to thick - walled configurations (up to 1" or more) for high - pressure and high - temperature scenarios.
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Similar diameter and wall - thickness availability as TP304. Dimensions are carefully selected based on the application's pressure, temperature, and flow - rate demands.
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Offered in a wide spectrum of diameters and wall thicknesses to meet diverse industrial needs. Sizing is engineered to handle various operating conditions.
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Pressure Ratings
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Can endure high pressures, usually up to several thousand pounds per square inch (psi), depending on factors such as diameter, wall thickness, and temperature. For example, a standard - sized TP304 pipe with a particular wall thickness might have a pressure rating of 1500 - 2500 psi at room temperature.
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Capable of withstanding significant pressures. The pressure rating is determined by the pipe's dimensions and the material properties of TP321H. It can handle pressures comparable to or slightly higher than TP304 in some cases, especially in high - temperature applications.
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Also has high - pressure capabilities. The pressure rating is designed to meet the requirements of applications like high - pressure steam lines or petrochemical pipelines, with values varying based on dimensions and service conditions.
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Pipe Type
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Seamless construction is the norm for TP304 pipes. This construction method, achieved by piercing a solid billet of stainless steel, provides excellent integrity and is well - suited for applications where high - pressure resistance and leak - tightness are crucial.
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Seamless pipes are common for TP321H due to their superior strength and reliability, especially in high - temperature environments. The seamless nature helps maintain the pipe's performance under thermal stress.
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Seamless TP347 pipes are preferred for applications requiring high - integrity and resistance to pressure and temperature. Their seamless construction ensures long - term durability.
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3. Material Properties
3.1 Chemical Composition
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Element
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TP304
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TP321H
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TP347
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Carbon (C)
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≤0.08
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0.04 - 0.10
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≤0.08
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Chromium (Cr)
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18.0 - 20.0
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17.0 - 19.0
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17.0 - 19.0
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Nickel (Ni)
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8.0 - 10.5
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9.0 - 12.0
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9.0 - 13.0
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Titanium (Ti)
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-
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5 x C - 0.70
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-
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Niobium (Nb)
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-
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-
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10 x C - 1.10
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3.2 Mechanical Properties
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Property
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TP304
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TP321H
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TP347
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Tensile Strength
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515 - 795 MPa
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515 - 795 MPa
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515 - 795 MPa
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Yield Strength
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≥205 MPa
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≥205 MPa
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≥205 MPa
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Elongation
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≥40%
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≥35%
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≥35%
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- TP304: A widely used austenitic stainless steel, TP304 offers good general corrosion resistance due to its chromium and nickel content. The relatively low carbon content helps prevent carbide precipitation to some extent, maintaining corrosion resistance in welded joints.
- TP321H: The addition of titanium in TP321H stabilizes the carbon in the steel. This prevents the formation of chromium carbides, which can cause intergranular corrosion. The "H" grade indicates higher carbon content, which improves high - temperature strength, making it suitable for applications involving long - term exposure to elevated temperatures.
- TP347: Niobium in TP347 serves a similar function to titanium in TP321H. It stabilizes the carbon, preventing carbide precipitation and enhancing the pipe's resistance to intergranular corrosion. This makes TP347 suitable for high - temperature applications where carbide precipitation could otherwise compromise the material's integrity.
4. Applications
- Food and Beverage Industry
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- TP304: Extensively used for transporting food - grade fluids such as water, milk, juices, and beer. Its smooth surface and corrosion resistance make it easy to clean and maintain, ensuring the purity of the transported products.
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- TP321H: While less common than TP304 in this industry, it can be used in equipment where high - temperature processing of food products occurs, like in some heat - sterilization processes. Its high - temperature stability ensures the equipment's integrity during such operations.
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- TP347: Similar to TP321H, TP347 can be used in high - temperature food - processing applications, especially those where long - term exposure to elevated temperatures is involved.
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- TP304: Ideal for transporting pharmaceutical ingredients, process fluids, and purified water. Its corrosion resistance and hygienic properties help meet the strict cleanliness and quality requirements of the pharmaceutical manufacturing process.
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- TP321H: Employed in equipment and piping systems that are subject to high - temperature sterilization processes. The titanium - stabilized structure allows it to withstand the thermal stress without significant loss of mechanical properties, ensuring the safety and integrity of pharmaceutical products.
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- TP347: Also suitable for pharmaceutical applications where high - temperature resistance and resistance to intergranular corrosion are important, such as in certain chemical - reaction vessels during pharmaceutical production.
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- TP304: Suitable for transporting a variety of non - highly aggressive chemicals, including mild acids, alkalis, and some organic solvents. However, its corrosion resistance may be limited in highly corrosive chemical environments.
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- TP321H: Used in chemical plants where the pipes are exposed to high - temperature chemical reactions or where there is a need for a material that can resist carbide precipitation during long - term high - temperature service.
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- TP347: Due to its niobium - stabilized structure, TP347 is often used in chemical applications involving high - temperature and corrosive conditions, such as in the production of certain polymers or in the handling of chemicals that could cause intergranular corrosion in other stainless - steel grades.
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- TP304: Can be used in non - critical cooling water systems in power plants. It can withstand the normal corrosion caused by water and some additives used in the cooling process.
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- TP321H: In power plants, TP321H is used in high - temperature sections of boilers and superheaters. Its high - temperature strength and resistance to creep make it suitable for withstanding the harsh conditions in these components.
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- TP347: Similar to TP321H, TP347 is used in high - temperature sections of power - generation equipment, such as in the piping systems for hot steam, where its resistance to high - temperature oxidation and intergranular corrosion is crucial for reliable operation.
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- TP304: Used in some onshore applications for transporting non - corrosive or mildly corrosive fluids and gases, such as in certain natural gas pipelines.
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- TP321H: Utilized in high - temperature sections of refineries, such as in pipelines carrying hot oil or in equipment exposed to elevated temperatures during the refining process.
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- TP347: Also finds application in the oil and gas industry, particularly in high - temperature and corrosive environments, like in pipelines transporting fluids with high sulfur content or in equipment used in oil - well downhole applications where high - temperature resistance is required.
5. Manufacturing Process
5.1 Billet Preparation
For all three grades (TP304, TP321H, and TP347), a solid billet of the appropriate stainless - steel material is selected. The billet is heated to a suitable temperature range, typically around 1100 - 1200 °C. This heating process makes the material more malleable, facilitating the subsequent forming operations.
5.2 Piercing
A piercing process is carried out on the heated billet. A pointed mandrel is forced through the center of the billet, creating a hollow tube. Precise control of this process is essential to achieve the desired inside diameter and wall thickness of the pipe.
5.3 Rolling and Sizing
The pierced tube is then passed through a series of rolling mills. These mills gradually reduce the wall thickness and increase the length of the tube while maintaining the desired diameter. Sizing operations are performed to ensure that the final pipe dimensions match the specified standards precisely.
5.4 Surface Treatment
- Pickling: All three types of pipes may undergo pickling. They are immersed in an acid solution, usually a mixture of nitric and hydrofluoric acids. Pickling helps remove oxide layers, scale, and impurities from the surface of the pipe, exposing the fresh, corrosion - resistant stainless - steel surface and enhancing its overall corrosion resistance.
- Passivation: After pickling, passivation is often carried out. The pipes are treated with a solution, such as nitric acid, to form a thin, protective oxide film on the surface. This oxide film further improves the corrosion resistance of the stainless steel by acting as a barrier against corrosive agents.
6. Quality Control
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- Chemical Analysis: Spectroscopy techniques are used to verify that the chemical composition of the incoming stainless - steel billets for each grade (TP304, TP321H, TP347) meets the specified standards. This ensures that the pipes have the correct alloying elements in the right proportions for their intended performance.
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- Mechanical Testing: Tensile tests are conducted to measure the tensile strength, yield strength, and elongation of the material. Hardness tests are also performed to ensure that the material has the appropriate hardness for its application. Impact tests may be carried out to assess the material's toughness, especially for applications where the pipes may be subject to sudden impacts.
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- External and Internal Dimensions: Calipers, micrometers, and laser - based measuring devices are used to measure the outside diameter, inside diameter, and wall thickness of the pipes. The measured dimensions are compared to the tolerances specified in relevant industry standards (such as ASTM or ASME standards) to ensure compliance.
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- Straightness and Ovality: The straightness of the pipes is checked using straight - edge tools or laser - alignment systems. Ovality, which refers to the deviation of the pipe's cross - section from a perfect circle, is measured to ensure that the pipes can be properly installed and connected.
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- Visual Inspection: The surface of the pipes is visually inspected for any visible defects such as cracks, pits, scratches, or inclusions. This is the first line of quality control to identify any obvious manufacturing flaws.
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- Non - Destructive Testing (NDT): Methods such as ultrasonic testing (UT), radiographic testing (RT), magnetic particle inspection (MPI), and penetrant testing (PT) are used to detect internal and surface - breaking defects that are not visible to the naked eye. UT can detect internal flaws like voids or inclusions, while RT can provide detailed images of the internal structure of the pipe to identify any defects. MPI and PT are used to detect surface - breaking defects, with MPI being suitable for ferromagnetic materials and PT being applicable to non - ferromagnetic materials.
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- Hydrostatic Testing: Pipes are filled with water and subjected to a specified pressure, usually higher than the rated working pressure, for a certain period. The pipes are then inspected for any signs of leakage or deformation. Hydrostatic testing is a common method to ensure the integrity of the pipes and their ability to withstand the pressure in service.
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- Pneumatic Testing: In some cases, especially for pipes that cannot be filled with water (e.g., those used in gas - only applications), pneumatic testing is performed. The pipes are filled with air or an inert gas and pressurized to a specified level. The pressure is monitored for any drop, which could indicate a leak. Pneumatic testing requires careful safety precautions due to the potential for explosive decompression if a failure occurs.
7. Advantages
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- TP304: Offers good general corrosion resistance in a variety of environments, making it suitable for many applications where mild corrosion protection is required.
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- TP321H: Its titanium - stabilized structure provides excellent resistance to carbide precipitation at high temperatures, ensuring reliable performance in high - temperature applications.
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- TP347: The niobium - stabilized structure gives TP347 good resistance to intergranular corrosion, especially in high - temperature and corrosive environments.
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- All three grades have sufficient tensile strength, yield strength, and elongation to withstand the mechanical stresses associated with fluid flow, pressure, and temperature changes in various applications.
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- TP304 is highly suitable for applications in the food and beverage and pharmaceutical industries due to its smooth surface, which prevents the build - up of bacteria and contaminants.
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- These pipes are available in a wide range of sizes and can be used in diverse industries, from food and beverage to power generation and oil and gas.
8. Conclusion
Seamless TP304, TP321H, and TP347 stainless steel pipes are essential components in a wide range of industries. Their unique material properties, such as corrosion resistance, high - temperature stability, and good mechanical strength, make them suitable for diverse applications. However, their relatively high cost and limitations in extreme conditions must be carefully considered when selecting the appropriate pipe for a specific project. By understanding their specifications, material properties, manufacturing processes, and quality control measures, engineers and industry professionals can make informed decisions to ensure the safe and efficient operation of piping systems.
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